This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. K-beta XES data have been obtained on a series of Fe(II) and Fe(III) model complexes in order to develop an understanding of the changes which occur in the Kbeta1,3 (3p-1s) and Kbeta2,5 (valences to 1s) emission spectra as a function of spin state, oxidation state and local structure. Of particular interest are the Kbeta? crossover features which are empirically correlated to a ligand 2s to 1s transition, and as such may be used to differentiate carbon from nitrogen from oxygen. Analyses of these data are currently underway. In addition, preliminary data on the MoFe protein of nitrogenase and the delta-nifB mutant have been obtained and demonstrate the feasibility of these methods for investigation of dilute protein systems.